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// This is based on https://github.com/smol-rs/async-io
// with adaptations by:
//
// Copyright (C) 2021 François Laignel <fengalin@free.fr>
//
// Take a look at the license at the top of the repository in the LICENSE file.
use futures::stream::Stream;
use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll, Waker};
use std::time::{Duration, Instant};
use super::Reactor;
/// A future or stream that emits timed events.
///
/// Timers are futures that output a single [`Instant`] when they fire.
///
/// Timers are also streams that can output [`Instant`]s periodically.
#[derive(Debug)]
pub struct Timer {
/// This timer's ID and last waker that polled it.
///
/// When this field is set to `None`, this timer is not registered in the reactor.
id_and_waker: Option<(usize, Waker)>,
/// The next instant at which this timer fires.
when: Instant,
/// The period.
period: Duration,
}
impl Timer {
/// Creates a timer that emits an event once after the given duration of time.
///
/// When throttling is activated (i.e. when using a non-`0` `wait`
/// duration in `Context::acquire`), timer entries are assigned to
/// the nearest time frame, meaning that the delay might elapse
/// `wait` / 2 ms earlier or later than the expected instant.
///
/// Use [`Timer::after_at_least`] when it's preferable not to return
/// before the expected instant.
pub fn after(duration: Duration) -> Timer {
Timer::at(Instant::now() + duration)
}
/// Creates a timer that emits an event once after the given duration of time.
///
/// See [`Timer::after`] for details. The event won't be emitted before
/// the expected delay has elapsed.
#[track_caller]
pub fn after_at_least(duration: Duration) -> Timer {
Timer::at_least_at(Instant::now() + duration)
}
/// Creates a timer that emits an event once at the given time instant.
///
/// When throttling is activated (i.e. when using a non-`0` `wait`
/// duration in `Context::acquire`), timer entries are assigned to
/// the nearest time frame, meaning that the delay might elapse
/// `wait` / 2 ms earlier or later than the expected instant.
///
/// Use [`Timer::at_least_at`] when it's preferable not to return
/// before the expected instant.
pub fn at(instant: Instant) -> Timer {
Timer::interval_at(instant, Duration::MAX)
}
/// Creates a timer that emits an event once at the given time instant.
///
/// See [`Timer::at`] for details. The event won't be emitted before
/// the expected delay has elapsed.
#[track_caller]
pub fn at_least_at(instant: Instant) -> Timer {
Timer::interval_at_least_at(instant, Duration::MAX)
}
/// Creates a timer that emits events periodically.
pub fn interval(period: Duration) -> Timer {
Timer::interval_at(Instant::now() + period, period)
}
/// Creates a timer that emits events periodically, starting after `delay`.
///
/// When throttling is activated (i.e. when using a non-`0` `wait`
/// duration in `Context::acquire`), timer entries are assigned to
/// the nearest time frame, meaning that the delay might elapse
/// `wait` / 2 ms earlier or later than the expected instant.
pub fn interval_delayed_by(delay: Duration, period: Duration) -> Timer {
Timer::interval_at(Instant::now() + delay, period)
}
/// Creates a timer that emits events periodically, starting at `start`.
///
/// When throttling is activated (i.e. when using a non-`0` `wait`
/// duration in `Context::acquire`), timer entries are assigned to
/// the nearest time frame, meaning that the delay might elapse
/// `wait` / 2 ms earlier or later than the expected instant.
///
/// Use [`Timer::interval_at_least_at`] when it's preferable not to return
/// before the expected instant.
pub fn interval_at(start: Instant, period: Duration) -> Timer {
Timer {
id_and_waker: None,
when: start,
period,
}
}
/// Creates a timer that emits events periodically, starting at `start`.
///
/// See [`Timer::interval_at`] for details. The event won't be emitted before
/// the expected delay has elapsed.
#[track_caller]
pub fn interval_at_least_at(start: Instant, period: Duration) -> Timer {
Timer {
id_and_waker: None,
when: start + Reactor::with(|reactor| reactor.half_max_throttling()),
period,
}
}
/// Sets the timer to emit an en event once after the given duration of time.
///
/// Note that resetting a timer is different from creating a new timer because
/// [`set_after()`][`Timer::set_after()`] does not remove the waker associated with the task
/// that is polling the timer.
pub fn set_after(&mut self, duration: Duration) {
self.set_at(Instant::now() + duration);
}
/// Sets the timer to emit an event once at the given time instant.
///
/// Note that resetting a timer is different from creating a new timer because
/// [`set_at()`][`Timer::set_at()`] does not remove the waker associated with the task
/// that is polling the timer.
pub fn set_at(&mut self, instant: Instant) {
Reactor::with_mut(|reactor| {
if let Some((id, _)) = self.id_and_waker.as_ref() {
// Deregister the timer from the reactor.
reactor.remove_timer(self.when, *id);
}
// Update the timeout.
self.when = instant;
if let Some((id, waker)) = self.id_and_waker.as_mut() {
// Re-register the timer with the new timeout.
*id = reactor.insert_timer(self.when, waker);
}
})
}
/// Sets the timer to emit events periodically.
///
/// Note that resetting a timer is different from creating a new timer because
/// [`set_interval()`][`Timer::set_interval()`] does not remove the waker associated with the
/// task that is polling the timer.
pub fn set_interval(&mut self, period: Duration) {
self.set_interval_at(Instant::now() + period, period);
}
/// Sets the timer to emit events periodically, starting at `start`.
///
/// Note that resetting a timer is different from creating a new timer because
/// [`set_interval_at()`][`Timer::set_interval_at()`] does not remove the waker associated with
/// the task that is polling the timer.
pub fn set_interval_at(&mut self, start: Instant, period: Duration) {
// Note: the timer might have been registered on an Executor and then transfered to another.
Reactor::with_mut(|reactor| {
if let Some((id, _)) = self.id_and_waker.as_ref() {
// Deregister the timer from the reactor.
reactor.remove_timer(self.when, *id);
}
self.when = start;
self.period = period;
if let Some((id, waker)) = self.id_and_waker.as_mut() {
// Re-register the timer with the new timeout.
*id = reactor.insert_timer(self.when, waker);
}
})
}
}
impl Drop for Timer {
fn drop(&mut self) {
if let Some((id, _)) = self.id_and_waker.take() {
Reactor::with_mut(|reactor| {
reactor.remove_timer(self.when, id);
});
}
}
}
impl Future for Timer {
type Output = ();
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
match self.poll_next(cx) {
Poll::Ready(Some(_)) => Poll::Ready(()),
Poll::Pending => Poll::Pending,
Poll::Ready(None) => unreachable!(),
}
}
}
impl Stream for Timer {
type Item = ();
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
Reactor::with_mut(|reactor| {
if Instant::now() + reactor.half_max_throttling() >= self.when {
if let Some((id, _)) = self.id_and_waker.take() {
// Deregister the timer from the reactor.
reactor.remove_timer(self.when, id);
}
let when = self.when;
if let Some(next) = when.checked_add(self.period) {
self.when = next;
// Register the timer in the reactor.
let id = reactor.insert_timer(self.when, cx.waker());
self.id_and_waker = Some((id, cx.waker().clone()));
}
Poll::Ready(Some(()))
} else {
match &self.id_and_waker {
None => {
// Register the timer in the reactor.
let id = reactor.insert_timer(self.when, cx.waker());
self.id_and_waker = Some((id, cx.waker().clone()));
}
Some((id, w)) if !w.will_wake(cx.waker()) => {
// Deregister the timer from the reactor to remove the old waker.
reactor.remove_timer(self.when, *id);
// Register the timer in the reactor with the new waker.
let id = reactor.insert_timer(self.when, cx.waker());
self.id_and_waker = Some((id, cx.waker().clone()));
}
Some(_) => {}
}
Poll::Pending
}
})
}
}
#[cfg(test)]
mod tests {
use std::time::{Duration, Instant};
use super::Timer;
use crate::runtime::executor::Scheduler;
const MAX_THROTTLING: Duration = Duration::from_millis(10);
const DELAY: Duration = Duration::from_millis(12);
#[test]
fn delay_for() {
gst::init().unwrap();
let handle = Scheduler::start("delay_for", MAX_THROTTLING);
let elapsed = futures::executor::block_on(handle.spawn(async {
let now = Instant::now();
Timer::after(DELAY).await;
now.elapsed()
}))
.unwrap();
// Due to throttling, timer may be fired earlier
assert!(elapsed + MAX_THROTTLING / 2 >= DELAY);
}
#[test]
fn delay_for_at_least() {
gst::init().unwrap();
let handle = Scheduler::start("delay_for_at_least", MAX_THROTTLING);
let elapsed = futures::executor::block_on(handle.spawn(async {
let now = Instant::now();
Timer::after_at_least(DELAY).await;
now.elapsed()
}))
.unwrap();
// Never returns earlier than DELAY
assert!(elapsed >= DELAY);
}
#[test]
fn interval() {
use futures::prelude::*;
gst::init().unwrap();
let handle = Scheduler::start("interval", MAX_THROTTLING);
let join_handle = handle.spawn(async move {
let start = Instant::now();
let mut interval = Timer::interval(DELAY);
interval.next().await;
// Due to throttling, timer may be fired earlier
assert!(start.elapsed() + MAX_THROTTLING / 2 >= DELAY);
interval.next().await;
// Due to throttling, timer may be fired earlier
assert!(start.elapsed() + MAX_THROTTLING >= 2 * DELAY);
});
futures::executor::block_on(join_handle).unwrap();
}
}
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